1. Field of the Invention
The present invention is broadly concerned with a rupture disc assembly having the characteristics of resistance to high burst pressures in one direction, while permitting rupturing under the influence of relatively low burst pressures in the opposite direction. More particularly, it is concerned with such a rupture disc assembly having particular utility in projectiles fired from hand held weapons in order to permit staged ignition of the propellant in the projectile, so that weapon can be used without fear of injuring the user.
2. Description of the Prior Art
Rupture disc assemblies have been used in the past in many contexts requiring rapid discharge or venting of materials. To give but one example, certain types of fire or explosion suppression apparatus include a pressurized tank of suppressant material along with a rupturable disc assembly sealing the material tank; when a hazard is sensed through a remote sensing mechanism, the disc assembly is ruptured, typically through the use of explosive charge, in order to permit the pressurized suppressant material to rapidly pass from the tank and into the area to be protected. Such rupture disc assemblies include a circular, concavo-convex metallic frangible rupture disc, which in many instances is scored to facilitate rupture thereof along predetermined lines of weakness. However, it will be perceived that disc assemblies of the foregoing type are designed to withstand the pressure condition exerted by the material within the suppressant tank, and normally the pressure conditions against the remote face of the frangible disc are at atmospheric or essentially unchanging, and in no event do pressure conditions against this remote face alter the burst characteristics of the overall assembly.
In recent years a number of hand held anti-tank field weapons have been developed for use by infantry troops against tanks or other armored vehicles. Generally speaking, these weapons include an elongated firing tube and firing mechanism, along with armor-piercing projectiles to be fired. The projectiles include a forward armor-piercing head, along with a solid propellant which is ignited when the weapon is fired. In order to be effective, such projectiles must achieve relatively high muzzle velocity, and hence the amount and type of propellant used with the projectile is an important consideration. However, in order to achieve desirable muzzle velocities, relatively high recoil forces are likewise necessarily developed. In the case of hand held weapons though, there is a limit to the magnitude of recoil forces which can be absorbed by the user, and this in turn has tended to place a maximum limit upon projectile propellant, and hence muzzle velocity.